We propose to study the repertoire of the immune response localized to tissues at sites of inflammation. These studies shall focus on the host response to allografts as demonstrated by the cells which can be propagated directly from biopsy tissue of grafts undergong episodes of cellular rejection. The ability of Interleukin 2 (IL2) to provide a mitogenic stimulus to "activated" T lymphocytes permits the outgrowth of host cells, from allograft tissue, which have been stimulated by the gtaft antigens. We shall determine the surface phenotype of tissue infiltrating cells in comparison to blood lymphocytes from the same patients and test the function and specificity of these cells in mixed lymphocyte and cell mediate lympholysis assays. Subsets of tissue infiltrating lymphocytes will be isolated by sorting on a FACS 440 by two color parameters in order to select functionally distinct cell types and determine their interactive roles in allograft recognition and destruction (or tolerance). Clones of tissue-infiltrating cells will be isolated to determine on a single cell level the fine specificity of alloreactions in transplant recipients, as well as interactional events between individual clones. Finally, we propose to use Southern blotting techniques in order to assess diversity, or clonal dominace of the immune response in situ. The cDNA probes now available to assist in the dissection of the T lymphocyte repertoire offer the capacity to correlate dominant patterns of genetic rearrangement with specificity and function of the cells which show restricted, or identical patterns of gene rearrangement for the T lymphocyte receptor. While the studies will focus on the allograft, preliminary evidence is presented which suggests the applicability of the techniques described for dissecting the immune response to other inflammatory stimuli, including auto-immune disorders and tumors.